Endemism

 

Species which are spread over a wide area or in different ecological conditions are said to be cosmopolitan. Some of them, called endemics are restricted to their distribution to a small region..

The term 'endemism' was coined by A.P. de candolle (1855) for the distribution of an organism in a limited geographical area

The phenomenon of restricted distribution of living organisms associated with some geographical or ecological factors is called endemism.

Among endemics, some species exhibit very localized distribution such as in small islands or mountain peaks and are called local endemics.

Some species may show restricted distribution but cover large areas in course of time. This is called expanding or progressive endemics.

 Endemism can be at family, genera or species levels.

Endemic families are the ones which grow only in a particle province of a country or continent. For example Cerciphyllaceae represented by two species in China. Davidiaceae is represented in Asia, Arachiaceae and Bruniaceae are represented by three species each in South Africa.

 Endemic Genera are found in a particular region or country isolated from other areas. Thus South Africa has 500 endemic genera constituting 30% of total genera in that region. Similarly, Australia with 40%, Srilanka with 20% and India with 33% have endemic genera.

 Endemic Species: Species restricted to a particular region are referred to as endemic species. Infact in the world many species are endemics to a particular region. In India nearly 12,760 species are endemic.

 Categories of Endemism:

There are following two types of endemics –

1. Paleo endemic or epibiotic or relics: these endemics are supposed to have been the remnants of a once widely distributed taxon in the past, e.g., Gingo biloba, Sequoia semipervivens.

 2. Neoendemics or micro endemics : these endemic taxa are supposed to have evolved only during the recent times and did not have sufficient time to extend their range of distribution.

 Endemism in India

About 4,900 species of flowering plants or 33% of the recorded flora are endemic to the country These are distributed over 141 genera belonging to 47 families. These are concentrated in the floristically rich areas of North-East India, the Western Ghats, North-West Himalaya and the Andaman & Nicobar Islands.

The Western Ghats and the Eastern Himalaya are reported to have 1,600 and 3,500 species of flowering plants, respectively. These areas constitute two of the 18 hot spots identified in the world. It is estimated that 62% of the known amphibian species are endemic lo India of which majority occur in Western Ghats. Nearly 50% of the lizards found in India are endemic

 

Endemic Species of India:

Rhododendron (Ericaceae),

Beaumontia grandiflora (Apocynaceae),

Eleusine coracana (Poaceae),

Caryota urena (Arecaceae),

Aegle marmelos (Rutaceae),

Crotolaria juncea (Fabaceae),

Ficus religiosa (Moraceae), and 

Seasamum indicum (Pedaliaceae).